Date of Graduation
Statler College of Engineering and Mineral Resources
Keith A. Heasley.
The recent Sago mine disaster has highlighted the need to fundamentally analyze the practical detection limitations of a mine rescue seismic system (Heasley, 2006). In various field tests, it was discovered that the surface peak particle velocity resulting from the trapped miner who pounds on the mine roof becomes undetectable past a certain distance from the surface geophones. In order to provide the mine rescuer the understanding of the exact extent of this distance; and the foreknowledge about the excepted magnitude of the surface peak particle movement in terms of: depth, geology and offset angle, this study was performed.;To achieve this goal, the following three major components were investigated: 1) the roof displacement resulting from the momentum of the impact of the signaling device when it hits the roof, 2) the pounding factor that relates the pounding instruments (sledgehammer or crib block) to the frequency and amplitude of the seismic signal, and 3) the attenuation of the displacement pulse as it moves through the overburden to the surface. To obtain these values, a parallel study of theoretical and experimental work was done (because of the uncertainties still associated with the mechanics of the roof momentum). In the theoretical analysis, a numerical model of the expected seismic attenuation of a given mine site was developed using an EXCEL spreadsheet. This model uses mine specific geology with the appropriate seismic parameters and vertical and horizontal offset distances to determine the expected attenuation. For the estimate of the pounding factor, the numerical modeling of the 4-West Mine where a field test took place was done to determine the seismic attenuation of the mine; and then the peak particle movements that were recorded during the seismic field experiment were back-analyzed to estimate the pounding factor.;With this simplified numerical analysis of the seismic attenuation and the representative' values for the pounding device pounding factor; the mine rescuer will be able to determine: 1) the expected magnitude of the surface peak particle movement, 2) the limiting distance where the signal would likely become undetectable, and 3) the chance of detecting a miner's signal with respect to the background noise level, and the appropriate steps to follow (either to implements appropriate procedures in order to reduce the noise level or to redirect the rescue efforts). It is believed that the information itemized above will be very useful to facilitate the optimization of the future mine rescue seismic deployment plan.
Adebisi, Adeniyi A., "Calculating the Surface Seismic Signal from a Trapped Miner" (2012). Graduate Theses, Dissertations, and Problem Reports. 2282.